钾离子诱导的羔羊近端尿道收缩：去甲肾上腺素和不同钙内流途径的作用

Potassium-induced contraction in the lamb proximal urethra: involvement of norepinephrine and different calcium entry pathways.

作者信息

García-Pascual A, Costa G, Isla M, Jimenez E, García-Sacristán A

机构信息

Departamento de Fisiología Animal, Facultad de Veterinaria, Universidad Complutense de Madrid, Spain.

出版信息

J Pharmacol Exp Ther. 1991 Jan;256(1):127-34.

PMID:1671093

Abstract

The purpose of this work was to investigate the mechanisms involved in the peculiar biphasic response of the lamb urethral smooth muscle to high K+ solutions. The relative amplitude of the phasic and tonic components of the contraction and its reproducibility were dependent on the concentration of K+ used. Only concentrations higher than 80 mM (i.e., 120 mM) showed a tonic component greater in amplitude than the phasic one and manifested a tachyphylactic effect. Phentolamine (10(-6) M), prazosin (10(-6) M) and chemical denervation with 6-hydroxydopamine significantly inhibited the tonic component of the K+ (120 mM)-induced contraction, modifying its morphology. Reproducible contractions to K+ (120 mM) could be obtained in the presence of prazosin (10(-6) M) or cocaine (10(-6) M). The preparations were also shown to accumulate [3H]noradrenaline and release it upon depolarization with K+ (60 and 120 mM). Calcium removal inhibited the K+ (120 mM)-induced contraction. After addition of calcium (0.5-5 mM) the contractile activity was restored. Nifedipine (10(-6) M) and verapamil (10(-6) M) but not sodium nitroprusside (10(-6) M) significantly blocked the contractile response for calcium as well as the phasic component of the K+ contraction in calcium-containing medium. In preparations treated with prazosin (10(-6) M) the tonic component of the K+ (120 mM) contraction was more sensitive to nifedipine and removal of extracellular calcium than the phasic one.(ABSTRACT TRUNCATED AT 250 WORDS)

摘要

这项工作的目的是研究羔羊尿道平滑肌对高钾溶液独特双相反应所涉及的机制。收缩的相性和紧张性成分的相对幅度及其可重复性取决于所用钾离子的浓度。只有高于80 mM（即120 mM）的浓度才显示出紧张性成分的幅度大于相性成分，并表现出快速耐受性效应。酚妥拉明（10⁻⁶ M）、哌唑嗪（10⁻⁶ M）以及用6-羟基多巴胺进行化学去神经支配均显著抑制了钾离子（120 mM）诱导收缩的紧张性成分，改变了其形态。在存在哌唑嗪（10⁻⁶ M）或可卡因（10⁻⁶ M）的情况下，可获得对钾离子（120 mM）的可重复性收缩。这些制剂还显示能积累[³H]去甲肾上腺素，并在受到钾离子（60和120 mM）去极化时释放它。去除钙离子可抑制钾离子（120 mM）诱导的收缩。加入钙离子（0.5 - 5 mM）后，收缩活性得以恢复。硝苯地平（10⁻⁶ M）和维拉帕米（10⁻⁶ M）而非硝普钠（10⁻⁶ M）能显著阻断含钙培养基中对钙离子的收缩反应以及钾离子收缩的相性成分。在用哌唑嗪（10⁻⁶ M）处理的制剂中，钾离子（120 mM）收缩的紧张性成分比相性成分对硝苯地平和去除细胞外钙离子更敏感。（摘要截取自250字）